The murine major histocompatibility complex, H-2, serves as an experimental model wherein to investigate immunoregulatory gene control of cellular and humoral immunity. This research project seeks to investigate a structure-function relationship between H-2I gene products on T lymphocytes (Iat antigens) and regulatory gene expression in functionally identifiable T cell subsets. Our overall objectives are three-fold. First, we are producing anti-Iat serum in strain pairs that differ at I-A, I-B, I-J, I-E, and/or I-C using concanavalin A-stimulated thymocytes as immunogen. Iat antigens, their cellular and haplotype distribution, are being analyzed by serological techniques. Secondly, we are using negative selection techniques to correlate Iat antigen expression with immune T lymphocyte function. Finally, we are characterizing one or more of these structures by biochemical means. In this manner, we hope to gain insight into the mechanistic explanation for I-region gene control over immune function.